No one is allowed to criticize the government

False. The government rarely sets out explicit censorship guidelines, making it difficult to determine what gets censored and what doesn't. But, a Harvard University working paper on social media censorship, the most recent version of which was released in October, found that there is plenty of criticism of the government online.

The team downloaded nearly 3.7 million posts (mainly from BBS and blog platforms, not microblogs) from 1,400 social media services over six months in 2011 (a period that included the arrest of Ai Weiwei, protests in Inner Mongolia and Zengcheng, and deadly bombings in Fuzhou).

About 13 percent of all social media posts were censored.

The Harvard paper describes several thousands of posts they found containing scathing critiques of China.